Secondary combustion system for woodburning stove

Abstract

A secondary combustion system for a woodburning stove employs a concave shaped screen for dispersing exhaust gases. A mixing chamber is formed in an insulated conduit between the concave screen and a second planar screen. The planar screen is perforated to form a random array of flaps which increase the turbulence of the exhaust stream so that a secondary combustion of the exhaust gases is produced.

What is claimed is: 
     
       1. An improved secondary combustion system for combusting the exhaust gases in a woodburning stove comprising: an insulated conduit defining an exhaust passageway and having an intake opening and an exit opening;   dispersion means defining a plurality of apertures interposed across said passageway in the vicinity of the intake opening to disperse exhaust gases injected through the intake opening;   a primary mixing chamber formed in the exhaust passageway for mixing the dispersed exhaust gases;   restriction means defining a plurality of apertures interposed across said passageway and spaced from said dispersion means to increase the exhaust velocity and turbulence of the exhaust gases;   turbulence means to increase the turbulence in the exhaust gases exiting the restriction means; and   a secondary combustion chamber formed in the exhaust passageway between the restriction means and the exit opening for combusting the exhaust gases.   
     
     
       2. The combustion system of claim 1 wherein the dispersion means is a generally concave shaped screen. 
     
     
       3. The combustion system of claim 1 wherein the restriction means is a substantially planar screen extending generally transversely across the exhaust passageway. 
     
     
       4. The combustion system of claim 3 wherein the screen is a metallic sheet which is perforated to form apertures in a manner wherein perforated flap portions extend at an angle to the screen, the turbulence means being the flap portions. 
     
     
       5. The combustion system of claim 4 wherein the flap portions are angularly oriented to form a generally random array of flaps extending from the plane of the screen. 
     
     
       6. The combustion system of claim 1 wherein the dispersion means apertures are substantially uniformly dimensioned and uniformly distributed. 
     
     
       7. The combustion system of claim 1 wherein the restriction means apertures are substantially uniformly dimensioned and uniformly distributed. 
     
     
       8. The combustion system of claim 1 wherein the exhaust passageway has a longitudinally extending segment and a transversely extending segment, the dispersion means being located in the transverse segment. 
     
     
       9. An improved woodburning stove adaptable for combusting exhaust gases comprising: a firebox chamber;   an exhaust plenum means communicating with the firebox chamber and adapted for connecting with an exhaust flue;   an insulated passageway having an intake opening leading from said firebox chamber and an exit opening leading to the exhaust plenum means;   a generally concave shaped screen defining a plurality of apertures interposed across said passageway in the vicinity of the intake opening;   a generally planar screen spaced from said concave screen and interposed across said insulated passageway, said planar screen forming a plurality of apertures; and   an array of generally randomly oriented flaps located in the passageway and extending at an angle to the planar screen.   
     
     
       10. The stove of claim 9 wherein the insulated passageway includes a generally vertically extending portion and a transversely extending portion terminating at the intake opening. 
     
     
       11. The stove of claim 10 wherein the concave screen extends inwardly into the transverse portion. 
     
     
       12. The stove of claim 11 wherein the concave screen is formed from stainless steel and the apertures are substantially uniformly dimensioned and uniformly distributed in the screen. 
     
     
       13. The stove of claim 10 wherein the planar screen is located at an intermediate vertical position of said vertical portion and extends transversely across the insulated passageway to form a lower mixing chamber and an upper secondary combustion chamber. 
     
     
       14. The stove of claim 13 wherein the planar screen is formed from a sheet of metal by perforating the sheet to form apertures and bending the aperture perforate portions to form said flaps. 
     
     
       15. The stove of claim 13 further comprising a high temperature probe extending into said secondary combustion chamber. 
     
     
       16. The stove of claim 10 wherein the exhaust plenum means extends generally transversely from said insulated passageway. 
     
     
       17. A method for removing pollutants from an exiting exhaust stream of unconsumed oxygen and exhaust gases produced by the combustion of combustibles in a woodburning stove comprising: (a) dispersing the exhaust stream into a plurality of small stream segments flowing in divergent directions;   (b) recombining and intermixing the stream segments to form a more homogeneous mixture of the unconsumed oxygen and the exhaust gases;   (c) restricting the exiting of the exhaust stream downstream of the intermixing thereby accelerating the gas stream;   (d) imparting a turbulence to the accelerated gas stream thereby combusting the exhaust gases in the presence of the unconsumed oxygen.   
     
     
       18. The method of claim 17 wherein steps (a)-(d) are performed in a substantially thermally isolated environment. 
     
     
       19. The method of claim 17 wherein steps (c) and (d) are performed in close proximity to facilitate the combusting of the exhaust gases. 
     
     
       20. The method of claim 17 wherein the steps (a)-(d) are performed without the introduction of a secondary supply of oxygen.